Oscillator



June 21, 1938. 0,1 MCILVAINE I 2,121,607

OSCILLATOR Filed Feb. 16, 1935 [liven/ 001: OTcLn T M Hum inc;

dwwualffwwhmm ftiforme gg Patented June 21, 1938 h UNITED STATES PATENT OFFICE 2,121,607 OSCILLATOR Oran T. Mcllvaine, St. Charles, 111.

Application February 16, 1935, Serial No. 6,812

2 Claims. (Cl. 25027.5)

My invention relates to the control of electric interposed in series with the anode 20. I have currents, and includes among its objects and adindicated a condenser 48 bridging the contacts 24 vantages an improvement in control means parand 22, and a condenser 50 bridging the contacts ticularly useful in connection with the trans- 24 and 20.

formation of direct current to alternating current. The arrangement of Figure 4 is identical except 5 In the accompanying drawing: that, to secure more perfect symmetry of move- Figure 1 is a partly diagrammatic cross section ment, I employ two actuating coils. The coil 52 is of an oscillator according to the invention on connected in parallel with the contacts 22 and 24,

line l-l of Figure 2; and the coil 54 is connected in parallel with the Figure 2 is a section on line 22 of Figure 1; contacts 20 and 24. 10

Figure 3 is a diagram of a circuit employing the With this arrangement one of the coils is oscillator of Figures 1 and 2; always pulling the weight 28 in the direction of Figure 4 is a diagram of another circuit emthe contact with which the cathode 24 is not enploying the same oscillator; and gaged, and the actuating impulses and the move- Figure 5 is an enlarged detail showing a heated ment of the weight will be completely symmetri- 15 electrode. cal. I have also indicated a single condenser 56 In the embodiment of the invention selected bridged across contacts and 22 to steady the for illustration, the oscillator comprises an evacucurrent flow. ated bulb l0 provided with a plurality of termi- In Figure 5 I have indicated a construction 20 nals indicated at l2,/ l4, and i6 passing through identical with that of Figure 1 except that the the press iii. The terminals l2 and i6 have cathode 58 extends a little at 60, and the extenduplicate contact portions '20 and 22 lying on opsion lies inside a small heating coil 62 whereby posite sides of the central contact 24. The conthe temperature of the cathode may be raised. tact 24 is connected to the conductor l4 by a leaf With the clearances and emitter specified I have 5 spring 26 weighted at its outer end as by a been able to convert direct into alternating curweight 28. rent with a direct current input of watts and 30 is an actuating coil for the weight 28, which and an output of 28 watts. As the losses thus weight is of magnetic material. For most fremeasured include the hysteresis loss in the transquencies the coil 30 may be provided with a former and the di-electric losses in the entire 30 core 32. system, it is obvious that the energy wasted at 30 34 indicates the capsule containing the emitter. the contacts is extremely small. Another fact I have secured good results with caesium for the evidencing the high efficiency of the contacts as emitter, in which case the capsule may be a mesuch is that such a set can operate for long chanical mixture of metallic calcium and caesium periods without warming the bulb enough so that chloride. Discharge of the capsule results in the its warmth can be noticed, whereas a very small 35 formation of calcium chloride and metallic Wattage is adequate to raise the temperature of caesium in excess of that necessary to provide a such a. bulb until it becomes distinctly warm to caesium atmosphere inside the bulb. I have obthe hand. tained good results with caesium when the clear- Without stating that such is the case, I believe 4() ance between the contacts 20 and 22 is such that the explanation of the facts above recited to be when the contact 24 is against one of them, the that the caesium atmosphere accomplishes a maspace between the contact 24 and the other is of terial contamination of the contactlsurfaces with the order of magnitude of .006 inch. a layer of caesium that may or may not build up In Figure 3 Ihave indicated wiring for convertto a thickness of one molecule over the entire ing the direct current generated by the battery surface.v 5

36 into an oscillating current delivered from the This surface of caesium, or in large part secondary winding 38 of the transformer 40 and caesium, is well known to have a very low work suitable for the operation of an alternating curfunction, and even at room temperatures there is rent radio receiving set. The midpoint of the a material emission of electrons, most of which,

primary 42 is connected to the positive terminal in the absence of a steep potential gradient to ac- 50 of the battery 36, and the negative terminal is complish their withdrawal, describe an orbit/and connected directly through the conductor l4 to return to the contact surface in which they origithe cathode 24. The anode 22 is connected to one nated. The presence of such an emissive conend of the primary at 44, and the anode 20 is tact surface has two material effects on the connected to the other end at 46. The coil 30 is operation of the system as a whole. First, when 55 the contacts are in mechanical engagement, the microscopic and sub-microscopic clearances between most of the surfaces in ordinary mechanical contact are permeated with the electrons emitted and this greatly decreases the contact resistance. Second, as the cathode 24 moves away from one anode, the current flow is not chopped off with the abruptness that would occur in the absence of an emitter, but is reduced gradually during the removal of the cathode to a distance from the anode equal to the mean etlective orbit of the electrons. Similarly, as the cathode completes its traverse and approaches the other anode, the current flow between the cathode and the other anode is initiated materially in advance of mechanical contact and built up gradually.

If this theory is correct, the net result is that the elective forces tending to generate the oscillatory flux in the transformer are not imposed and discontinued abruptly in step by step fashion, but become eflective in accordance with a curve that will be a much closer approximation to a sine curve. This would contribute greatly, not only to the smoothness of the oscillator current issuing from the winding 38, but to the ease with which a condenser of suitable size can be made to tune the different parts of the circuit so that mechanical separation between the cathode and each anode occurs at a time when the relatively high irequency disturbance of the current flow caused by such separation will be a minimum.

Without further elaboration, the foregoing will so fully explain my invention that others may, by applying knowledge current at the time of such application, readily adapt the same for use under various conditions of service. It will, for instance, be obvious that any one of a number of other emitters might be employed and that one or more of the contacts 20, 22, and 24 may be heated to a greater or less degree to build up the emissivity of the contact surfaces to the extent found most advantageous; also that other substances such as inert gases at suitable pressures may be included in the filling for the bulb for various purposes.

I claim:

1. An oscillator comprising, in combination: a sealed bulb; a pair of spaced contacts therein; a third contact between said spaced contacts; means for oscillating said third contact between said spaced contacts; and an emitter in said tube, wherewith the contact surfaces are contaminated, said emitter being capable of emitting electrons at room temperature; the clearance between said contacts permitting said third contact a range of movement greater than, but of the same order of magnitude as, the mean efiective orbit for an electron originating in the surface of the cathode at room temperatures and under the potential gradients obtaining during normal operation.

'2. An oscillator comprising, in combination: a sealed bulb; a pair of spaced contacts therein; a third contact between said spaced contacts; means for oscillating said third contact between said spaced contacts; and an emitter in said tube, wherewith the contact surfaces are contaminated; the clearance between said spaced contacts permitting said third contact a range of movement of the order of magnitude of the distance through which the electronic emission from the cathode influences the effective resistance to current flow between said contacts; said oscillating means including a weight and a resilient connection between said weight and said third contact, permitting said weight'an excursion extending in both directions beyond the positions corresponding to engagement between said third contact and one of said pair of contacts.

ORAN T. McILVAINE. 

